An activity-based near-infrared glucuronide trapping probe for imaging β-glucuronidase expression in deep tissues

Area of Science:

• Biochemistry
• Molecular Imaging
• Chemical Biology

Background:

• Beta-glucuronidase is a key enzyme for reporter gene expression and prodrug activation.
• Near-infrared (NIR) probes are desirable for in vivo imaging due to deeper tissue penetration.
• Currently, NIR glucuronide probes for beta-glucuronidase activity are unavailable.

Purpose of the Study:

• To develop novel fluorescent probes for detecting beta-glucuronidase activity.
• To create both visible and NIR range probes for versatile imaging applications.
• To assess the efficacy of these probes in preclinical models.

Main Methods:

• Synthesis of two fluorescent probes: FITC-TrapG (visible) and NIR-TrapG (NIR range) using a difluoromethylphenol-glucuronide moiety.
• In vitro testing on purified beta-glucuronidase and beta-glucuronidase-expressing cells (CT26/mβG).
• In vivo imaging of subcutaneous and deep-seated tumors in preclinical models.

Main Results:

• FITC-TrapG showed selective trapping on beta-glucuronidase and expressing cells, not on controls.
• Activated FITC-TrapG did not inhibit enzyme activity and could label bystander proteins.
• Both probes imaged subcutaneous tumors; NIR-TrapG uniquely visualized deep liver tumors.

Conclusions:

• Developed novel TrapG-based fluorescent probes for beta-glucuronidase activity detection.
• NIR-TrapG is a promising tool for in vivo visualization of beta-glucuronidase activity, especially in deep tissues.
• These probes have potential applications in reporter gene imaging and cancer prodrug therapy.